1. Field of the Invention
The invention relates to a coaxial filter cigarette comprising a rod portion having an inner core of a material glowing substantially free of residue, in particular tobacco material, a sheath or wrapper for the inner core, an outer shell of a tobacco and/or non-tobacco material coaxially surrounding the inner core or its sheath or wrapper respectively and a sheath or wrapper for the outer shell as well as a filter portion.
2. Description of the Prior Art
A number of publications on so-called "coaxial smokable articles" exists, i.e. in particular coaxial cigars or cigarettes having an inner core which is surrounded by a shell or jacket of tobacco material. The basic principle of such a coaxial cigarette is known, for example, from French Patent Specification No. 998,556; here the inner core consists of tobacco of lower quality which is surrounded by an annular shell of tobacco of high quality. This makes it possible to achieve savings as regards the costs of the tobacco materials used.
Further designs of such coaxial cigarettes are disclosed in French Patent Specification No. 1,322,254, U.S. Pat. Nos. 3,614,956, 4,219,031, British Patent Specification No. 2,070,409, British Patent No. 1,086,443 and German Offenlegungsschrift No. 3,602,846. Furthermore, U.S. Pat. No. 3,356,094 discloses a coaxial cigarette having an inner hollow tube and an aerosol production zone with a narrow outlet; the making of this coaxial cigarette is, however, very complicated and thus expensive; moreover, the various components are separated from each other so that an unusual smoke pattern results.
Finally, a coaxial filter cigarette of the aforementioned type is known from the U.S. Pat. No. 281,640 and comprises a rod portion and a filter portion; the rod portion contains an inner core of a material glowing substantially free of residue, in particular tobacco material, a sheath or wrapper for the inner core, an outer shell of a tobacco and/or non-tobacco material coaxially surrounding the inner core or its sheath or wrapper, respectively, and a sheath or wrapper for the outer core.
The filter portion comprises a filter core, an air-impermeable sheath or wrapper for the filter core, a filter shell and a sheath or wrapper for the filter shell.
The basic principle of this coaxial filter cigarette resides in a distinction in the radial direction between two regions, that is the zone of the main heat source on the one hand and the zone in which the major part of the aerosol reaching the mouth of the smoker is produced on the other hand. The heat generating zone is in the outer shell and the aerosol producing zone is in the inner core of the rod portion.
In such a design of a coaxial filter cigarette the desired reduction of the secondary stream (smoke) is problematical and can be achieved only with great expenditure of time and expense. Moreover, such a coaxial filter cigarette has an inflammatory potential similar to that of a conventional cigarette.